A composition of acetic acid and a composition of acetic acid and RF3 effecting expression of DAF-16 in C. elegans, wherein the at least acetic acid and the RF3 polysaccharide is effective to increase the life-span of C. elegans or humans. A method of regulating DAF-16 expression, comprising: administering a composition comprising at least acetic acid and RF3 polysaccharide; providing the composition to at least one receptor on a surface of a cell; causing an increase in expression of DAF-16. A method for screening a series of compounds or constituents parts of compounds including some antioxidant vitamins, traditional herb medicines, and vinegars using C. elegans as a live organism model to examine to determine if they have an impact the lifespan of C. elegans and the underlying mechanism(s) thereof.